1. Field of the Invention
The invention relates to a device for spreading, compressing and guiding a running web of material.
2. The Prior Art
A device for guiding and spreading a running web of material is known from German Patent Application No. 42 13 208 C2. This device is formed by a roll that has a series of slats distributed over the circumference of the roll. These slats extend transversely in the direction in which the web is running, and parallel to the axis of the roll. The slats each extend from one end of the roll up to a center area. Within the area of the outer ends of the roll, control disks are provided and are connected to an end of each slat at the respective end of the roll via guide rods. These control disks can be swivelled by servo-drives that operate independently of the rotation of the roll. Therefore, the slats have a pushing movement in the longitudinal direction as the roll is completing one full rotation. This pushing movement displaces the material web sideways, with the material web being pulled over the slats.
By positioning both control disks at an acute angle in relation to one another, the displacement of the slats of both roll end areas is away from each other, so that the web of material is spread or compressed. However, openings are produced in this process in the center area between the aligned slats. These openings open and close in the course of one rotation of the roll. The openings pose a substantial risk of accidents especially while a new web of material is being threaded in because the operator""s finger may easily get caught in the openings. However, if the web of material is guided by belts, such belts may penetrate the openings and get into the space beneath a center slat end, causing the slat to be destroyed in the course of a rotation of the roll. This results in a loss of production and repair costs.
A guide device for a traveling web of material is also known from German Patent Application No. 34 30 218 C2. This guide device is formed by a roll and the longitudinally displaceable slats are disposed on the outer circumference of the roll. These slats are transversely displaced by a controlling device located on one side in the direction of travel of the material web. The slats extend over the entire width of the material web. This device is exclusively suited for guiding the material web without spreading or compressing it.
It is an object of the present invention to provide a device for spreading, compressing and guiding a running material web that is safer to operate and reduces the risk of accidents.
The device of the present invention is employed both for guiding and spreading or compressing a running web of material. The device comprises a rotating roll which is looped by the material web preferably at an angle between 90xc2x0 and 180xc2x0. On the roll, slats are provided that are distributed over the circumference of the roll and transversely extend in the direction of web travel. These slats are longitudinally displaceable on the roll and the displacement of the slats is accomplished by control devices. The running web of material is guided along by the slats and the slats are transversely displaced in the running direction of the web, and the web is displaced corresponding to the movement of the slats. A web running outside its nominal position can be returned to its correct position with great precision. Furthermore, to allow spreading of the material web, half of the slats have a higher adhesive power than the opposite half. Therefore, a slat can pull one half of the web, so that a spreading effect can be achieved in addition to the desired guiding effect. Owing to the difference in adhesive power of the two halves of the slats, the slats can extend transversely over the entire width of the web of material so that no division of the slats is required within the center area of the roll. Furthermore, since there is no division of the slats, no variable openings will occur between the slats. Furthermore, no belts can get caught or entangled between the slats, so that any destruction of slats is avoided.
The difference in adhesive power of the halves is preferably as high as possible to achieve good response of the halves of the material web to the movement of the slats. Finally, the advantage of the present invention is that the slats extending over the material web are substantially more stable than slats that are self-supporting at one end. Therefore, the slats are capable of supporting higher web pulling forces overall. The slats are also simply manufactured and with greater material savings. Due to the through-extending support of the material web over its entire width, the web is guided across the slats in a smooth manner without folds or waves. Furthermore, there is no risk that the ends of the slats may damage the underside of the material web in any way. To guide and spread the material web with the roll at the same time, it is necessary to control some of slats with one of the control devices and the remaining slats with another control device. Therefore, all jointly controlled slats are provided with the adhesive side located in the same slat area. This assures that the slats controlled by one control device engage only one of the two web halves in an adhesive manner, whereby the half of the web disposed on the opposite side is practically not influenced by the slats. Therefore, each control device can determine the run of the respective edge of the web substantially independent of the other control device. By moving the control devices in the same direction, it is possible to influence the guidance of the material web, and by moving the control devices in opposing directions, a spreading effect of the material web will occur.
To achieve the greatest possible response of the material web to the movement of the slats, it is preferred that half of each slat is coated with an adhesive. This adhesive surface provides for optimal transmission of the movement of the slats to the web of material, so that the movement of the material web along the slats substantially corresponds to the actual course of the respective edge of the web. However, the engagement area on the opposite side of the web is provided with a surface that has a sliding property along the material web. Therefore, the area of the oppositely disposed edge of the web is not influenced by the slats, which is particularly important when the material web is spread. For spreading, the two halves of the material web are pulled in opposite directions. However, each slat would basically pull both halves of the material web in the same direction. The surface of the slat is therefore provided with a sliding property on part of its surface area, so that the slat exert no force on the material web.
For simpler manufacturing of the slats, it is advantageous if the slats are provided with an adhesive coating. This coating may be arranged in a suitable recess of the slat, so that it will not substantially protrude beyond the surface of the slat. Alternatively, the adhesive coating can also be applied directly to the surface of the slats such that the adhesive coating remains adequately thin. The extra thickness formed on the surface of the slats can be used for engaging the material web in the area of the adhesive coating.
The adhesive coating preferably has a napped-like structure to achieve optimal adhesion of the material web to the adhesive coating.
In the event a wet web of material has to be guided or spread, it is advantageous if the adhesive coating is provided with channels for draining the liquid. The liquid contained in the material web is pressed into the adhesive coating by a tension force applied to the material web where it can drain via the drain channels. Draining the liquid provides improved adhesion of the web to the slat.
It is preferred that alternating slats are associated with the same control device. Therefore, an adhesive slat is followed by a sliding slat. This results in a control system for running and spreading the web that responds in a highly sensitive manner. In particular, it has been found that the guiding effect of the slats is enhanced if a sliding slat is provided between each two adhesive slats along one side of the web. This occurs because within the area of the sliding slat, the web is capable of compensating the differences in travel distance of the adhesive slats moving at different speeds by a relatively minor shear. On the other hand, if adhesive slats were to successively follow each other in direct sequence, a high shearing effect would be created on the material web. This shearing effect would cause folds in the web. However, the web generally slides to a minor degree across the adhesive coating to eliminate the shearing forces. This, however, reduces the guiding effect of the slats, which is avoided by the arrangement of the slats in the present invention.
To control the movement of the slats in the easiest and most precise manner, the control devices are formed by control disks which are connected with the slats via guide rods. The control disks are preferably pivot-mounted, rotating about an axis extending perpendicular to the axis of the roll. The control devices are not coupled to the rotational motion of the roll, but are stationary. Therefore, the slats connected with the control disks via the guide rods move away from the center of the roll during the first half of a rotation of the roll, and toward the center of the roll during the next half of the rotation of the roll. The material web loops around the roll only on a partial area, in which the slats move away from the center of the roll during the rotation of the roll. This results in a continual spreading, whereby the spreading effect can be adjusted in any desired manner by the angular position of the control disks.
To control the run of the material web, the control disks are controlled by a controlling device. Therefore, the control disks are pivoted at angular positions in relation to the axis of rotation of the roll by servo-drives. A controlling device influences the run of the web via the servo-drive and the angular position of the control disk and the movement of the slats.
To assure precise movement of the slats, the slats are supported in slide guides. These slide guides are useful in the area of the free ends of the slats to ensure that the material web is adequately supported on the slats over its entire width. The slide guides are kept stationary on the roll. This provides for undercut slide guides that prevent the slats from tilting away from the axis of the roll.
If the control devices each are controlled by a servo-drive, the spreading and guiding effects can be adjusted independently of each other and without manual intervention. It is also possible to control the positions of both edges of the web for achieving web guidance and control of the width of the web.